/fee"meuhr/, n., pl. femurs, femora /fem"euhr euh/.
1. Anat. a bone in the human leg extending from the pelvis to the knee, that is the longest, largest, and strongest in the body; thighbone. See diag. under skeleton.
2. Zool. a corresponding bone of the leg or hind limb of an animal.
3. Entomol. the third segment of the leg of an insect (counting from the base), situated between the trochanter and the tibia. See diag. under coxa.
[1555-65; < L: thigh]

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also called  thighbone 
 upper bone of the leg or hind leg. The head forms a ball-and-socket joint with the hip (at the acetabulum), being held in place by a ligament (ligamentum teres femoris) within the socket and by strong surrounding ligaments. In humans the neck of the femur connects the shaft and head at a 125° angle, which is efficient for walking. A prominence of the femur at the outside top of the thigh provides attachment for the gluteus medius and minimus muscles. The shaft is somewhat convex forward and strengthened behind by a pillar of bone called the linea aspera. Two large prominences, or condyles, on either side of the lower end of the femur form the upper half of the knee joint, which is completed below by the tibia (shin) and patella (kneecap). Internally, the femur shows the development of arcs of bone called trabeculae that are efficiently arranged to transmit pressure and resist stress. Human femurs have been shown to be capable of resisting compression forces of 800–1,100 kg (1,800–2,500 pounds).

 The femur in humans is long and relatively slender or delicate; in the great apes it is shorter, more curved, and more robust. The orangutan lacks a ligamentum teres femoris, allowing for nearly complete rotary action of the lower limb but decreasing strength and stability.

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Universalium. 2010.